The subject matter disclosed herein relates to heating, ventilation and air conditioning (HVAC) systems. More specifically, the subject matter disclosed herein relates to chillers.
As regulatory & industry trends continue to drive towards replacement of conventional HFC's like R134a of particular interest are the class of “low pressure refrigerants”, i.e. refrigerants that are near, or below atmospheric pressure at the boiling temperatures in a chiller. These have long been known to provide better thermodynamic cycle performance over medium (R134a) or higher (R410A) pressure refrigerants, due to their higher latent heats of vaporization and other thermodynamic properties. However, yet other thermodynamic properties such as vapor density or transport properties such as surface tension can reduce heat transfer performance and offset a significant portion of the thermodynamic cycle performance gains. Further, low pressure refrigerants have significantly greater specific volumes, resulting in the need for larger vapor spaces and pipes to connect the components of the chiller system. The larger vapor spaces and pipes are more costly and increase the volumetric footprint required to accommodate the chiller system.